York: Aldon Smith will seek treatment, leave team indefinitely

Aldon Smith sits on the bench as the clock winds down toward a loss to the Colts. (Carlos Avila Gonzalez/The Chronicle)

Niners CEO Jed York said All-Pro outside linebacker Aldon Smith would seek treatment, presumably for a substance-abuse problem, and would not be with the team when it visits the Rams on Thursday night in St. Louis.

York offered no timetable for Smith’s return. Smith, 23, was arrested at 7:02 a.m. for suspicion of DUI after his pickup slammed into a tree in a residential neighborhood in San Jose. It was the latest off-the-field incident for Smith, who was also arrested for DUI in January 2012 and stabbed at a party at his house 15 months ago.

“I’ll support our players as long as they’re willing to work towards getting better, and being better teammates, and being better member of the community,” York said. “And I believe Aldon wants to do that. And I will support him and I will stand by him as long as that’s what he’s willing to do … I believe Aldon wants to tackle this problem and we’re going to do everything we can do to help him with this.”

Smith addressed reporters after the 49ers’ 27-7 loss to the Colts at Candlestick Park. He exhaled deeply before speaking, without notes, for about 30 seconds. Before Smith spoke, 49ers public relations director Bob Lange said he would not take questions.

“First off, I wanted to apologize to the team, the organization, my family, everybody I let down,” Smith said. “I just wanted to let it be known that this is a problem and it’s something I will get fixed. And I will do everything within my power to make sure this never happens again. I also wanted to let everybody know that, once again, I’m sorry. Like I said, this won’t happen again.”

York said he met with Jim Harbaugh and general manager Trent Baalke regarding Smith’s playing status for Sunday. Smith didn’t miss a defensive snap, collected five tackles and no sacks. York said Smith wanted to play, and he suggested the 49ers allowed him to do so because of his willingness to seek treatment. Smith earns about $99,000 in base salary per game.

“Our opinion was sitting somebody down, and paying them to sit down, when they are going to seek treatment in the future didn’t seem like an appropriate punishment,” York said. “I k now it might not sound reasonable, but for Aldon to be able to face the media, face his teammates and take full responsibility for what he’s doing, we felt that was the best situation for Aldon himself. And for the team. And, ultimately, for the community at large. I realize people might not agree with that decision. That was the decision that we felt was best.”

Without Smith, either Dan Skuta or rookie Corey Lemonier, a third-round pick, will start in his place Thursday night. Skuta, who was an inside linebacker during his first four seasons in Cincinnati, has made four starts since entering the NFL as an undrafted free agent in 2009. The 49ers traded two outside linebackers — Parys Haralson and Cam Johnson — before the season opener.

The 49ers could also be without All-Pro inside linebacker Patrick Willis, who left Sunday’s game late in the third quarter with a groin injury. Willis declined an interview request after the game and the severity of his injury is not known.